1. Field of the Invention
The present invention relates to a vibration-damping assembly disposed between a prime mover as a source of vibration such as an internal combustion engine and a support for the prime mover, and more particularly to a vibration-damping assembly which is preferably mounted between a support and a prime mover in a portable working machine.
2. Description of the Prior Art
Generally, in a portable working machine, for instance, a vibration-damping assembly is mounted between an internal combustion engine or the like as a prime mover and a support to prevent the propagation of vibration caused by a prime mover such as an internal combustion engine to a worker, and various vibration-damping assembly have been proposed and put to practical use. One of the vibration-damping assembly is disclosed in Japanese Examined Utility Model Publication No. 9793/1988 and so on.
In conventional vibration-damping assembly, as described in the above-mentioned Publication, a vibration-damping rubber as a vibration-damping member or a coil spring is often independently used. However, a single vibration-damping member can not cover wide range of vibration, that is, the range of vibration that a single vibration-damping member sufficiently functions as it is narrow. For instance, it is difficult for vibration-damping rubber only to cover overall range of rotation of an internal combustion engine. On the other hand, a coil spring functions in wide range of vibration, however, the coil spring is susceptible to malfunction as time passes, that is, its durability is a problem.
Further, it is desirable to change the spring constant in accordance with the replacement of an internal combustion engine or members accompanying the engine to provide the best vibration-damping efficiency, however, in conventional vibration-damping assembly, the spring constant can not be changed, therefore, it is necessary to replace overall vibration-damping assembly, resulting in troublesome work and disadvantage in cost.